This invention relates to improvements in methods of image processing, in particular the processing of images as part of a lane detection apparatus or road profile prediction method and apparatus.
It is known to use a simple video camera to capture an image of a region of highway ahead of a vehicle. The camera comprises a two dimensional grid of detector pixels, each of which produces an output signal whose value is dependent on the intensity of the light falling on the pixel during a sampling period. The image output from the array is therefore a grey-scale image. It is then known to process the image to identify lane boundary markings, and from this determine the route of the highway. A suitable method of identifying the markings is taught in EP 1 057 141 B 1.
The applicant has appreciated that this works well in many countries, such as the UK, where the lane boundaries are marked by high contrast white lines on a dark coloured road surface. The white line is much lighter in colour than the road surface, and this shows up well in the grey scale image, making it relatively simple to detect lane boundaries. However, the applicant has appreciated that this does not work well when the lane boundary markings are not white. For instance, in Korea it is common to use yellow and blue markings for lane boundaries. When imaged using a grey scale imager, the lane boundaries are often indistinguishable from the road surface. The marking and road typically have the same, or very similar, lightness when considered in grey scale.